1. Field of the Invention
The invention relates to an assembly of a carrier and a shaped charge for use in an elongated perforating gun of the type generally used to perforate oil and gas wells. The invention particularly pertains to the manner in which the shaped charge is held in place relative to the carrier of the perforating gun.
2. Description Of The Prior Art
Perforating guns commonly used in wireline service operations for perforating an oil or gas well typically include an elongated cylindrical outer housing within which is received an elongated carrier which has a number of shaped charges in place in the carrier. The carrier is located relative to the housing so as to locate each of the shaped charges adjacent reduced thickness portions of the housing.
It is known in the prior art to utilize either triangular or hexagonal cross-section tubular carriers constructed to receive three 120.degree. circumferentially spaced shaped charges in a given horizontal plane. When a hexagonal carrier is utilized, longitudinally adjacent layers of charges may be rotated 60.degree. relative to each other to spread out the pattern of perforations along the length of well which is to be perforated.
Typically, the shaped charges have been held in place relative to the carrier by snap rings which interlock both with the outer case of the shaped charge and with the carrier.
Furthermore, a number of structures for attachment of shaped charges to the carrier have been developed.
For example, in U.S. Pat. No. 4,326,462 to Garcia et al., a plastic retaining chip fits over a shoulder of the outer case of the shaped charge. The plastic retaining clip includes flexible arms which snap into holes in the wall of the carrier.
Another arrangement is shown in U.S. Pat. No. 3,773,119 to Shore wherein a square cross-section flexible carrier tube has cut-out portions thereof which engage notches in the outer case of the shaped charge. Additionally, a threaded plug, received in the housing of the perforating gun, itself engages the shaped charge to snugly hold it in place within the housing.
Another example of a manner in which a shaped charge may be retained in place relative to a carrier is shown in U.S. Pat. No. 3,636,875 to Dodson wherein the shaped charge has spaced shoulders between which is received a wire-type frame member.
From these various examples just discussed, it is seen that the prior art has long recognized the need for a reliable means for retaining shaped charges in place within a carrier of a perforating gun. The present invention provides a much improved, very economical, reliable, and easily assembled construction for the assembly of a shaped charge with a carrier.